KeePassX might be of special interest to you, if the Mono trouble was the only thing bothering you. It's a native port of KeePass to Linux and MacOS X and, as you're running Ubuntu, even contained in the official (Ubuntu) repositories, so a simple
sudo apt-get install keepassx
will put it on your machine (and a corresponding start-icon into Accessories → KeePassX).
So how does it match your requirements?
- it should be very secure: Yes, it is. You can chose between either the Advanced Encryption Standard (AES) or the Twofish algorithm
- working in-browser autotype: It offers a feature called "AutoFill"
- configurable location of the data file: You have only one? You can have many :)
- password generation: Yes, with several options (see screenshot below)
- ability to categorize passwords into folders: Yes, we (s)can! See screenshot below.
Main window and password generator (click images for larger variants)
Additional benefits are the platform independency (you can even use your current database from KeePass with it, and can use the very same on Android, or wherever), a nice interface, user-defined symbols for groups and entries are possible (to make the items easier to identify), a quality indicator for chosen passwords; a search function, ...
Possible draw-backs might include its rigid structures for the records: it's clearly written with website logins in mind (URL, login, password, comments). I find it hard to use it for e.g. credit card or bank account information. Also, it only supports the KeePass 1.x (
.kbd) database format (a good thing when using the Android App "in sync", as that also is restricted to v1.x databases), not the newer v2.x
Also note note that the current stable version (0.4.3) was published 4 years ago and is no langer maintained. While KeePassX 2 seems to be actively developed, but it’s currently an alpha version. (thanks to unor for pointing this out)
P.S.: Definitly see Caleb's answer on my question here for more details and background on KeePassX and its latest versions!